BZOJ 1565. [NOI2009]植物大战僵尸


http://www.lydsy.com/JudgeOnline/problem.php?id=1565
https://www.byvoid.com/blog/noi-2009-pvz

拓扑排序 + 最大权闭合子图。


const int N = 600 + 3, M = N * N * 4;


struct Network_Flow{
    
    int D[N], hd[N], suc[M], to[M], cap[M];
    int n, m, s, t;
    
    inline void ae(int x, int y, int c){
        suc[m] = hd[x], hd[x] = m, to[m] = y, cap[m++] = c,
        suc[m] = hd[y], hd[y] = m, to[m] = x, cap[m++] = 0;
    }
    
    inline void aee(int x, int y, int c){
        suc[m] = hd[x], hd[x] = m, to[m] = y, cap[m++] = c,
        suc[m] = hd[y], hd[y] = m, to[m] = x, cap[m++] = c;
    }
    
#define v to[i]
#define c cap[i]
#define f cap[i^1]
    
    LL sap(){
        LL z=0; static int cnt[N],cur[N],pre[N];
        fill(D,D+n,n),fill(cnt,cnt+n,0);cnt[n]=n;
        int u=s;cur[s]=hd[s];while (D[s]){
#define i cur[u]
            if (u==t){
                int d=INF;for(u=s;u!=t;u=v)checkMin(d,c);
                z+=d;for(u=s;u!=t;u=v)f+=d,c-=d;u=s;
            }
#undef i
            int i;for(i=cur[u];i;i=suc[i]){
                if(D[u]+1==D[v]&&c){cur[u]=i,cur[v]=hd[v],pre[v]=u,u=v;break;}
            }
            if (!i){
                if (!--cnt[D[u]])break;
                D[u]=1;REP_G(i,u)if(c)checkMax(D[u],D[v]);--D[u];
                ++cnt[D[u]];if(u==s)cur[u]=hd[u];else u=pre[u];
            }
        }
        
        return z;
    }
    
    void init(int _n){
        n = _n; s = 0, t = n + 1; m = 2; n = t + 1;
        fill(hd, hd+n, 0);
    }
    
} G;
#undef v
#undef c
#undef f


VI _adj[N], adj[N]; int inD[N], scr[N], h[N], q[N] = {M}, op, cz, u, v;
int r, c, s, t, n, m, ans;

inline void add_edge(int x, int y){
    ++inD[y], _adj[x].PB(y);
}

inline int id(int x, int y){
    return x * c + y + 1;
}



#define v _adj[u][i]
void init(){
    RD(r, c);
    
    REP(i, r) REP(j, c){
        if (j != 0) add_edge(id(i, j), id(i, j-1));
        int t, x, y; RDD(scr[id(i, j)]);
        Rush RD(x, y), add_edge(id(i, j), id(x, y));
    }
    
    n = r * c;
    
    // Toposort ..
    
    op = 0;
    REP_1(i, n) if (!inD[i])
        q[++op] = i;
    
    while (op){
        u = q[op--];
        REP(i, SZ(_adj[u])){
            --inD[v];
            if (!inD[v])
                q[++op] = v;
        }
    }
    
    // Graph Initializing..
    
    
    G.init(n);
    
    REP_1(u, n) if (!inD[u]){
        
        if (scr[u] > 0){
            G.ae(G.s, u, scr[u]);
            ans += scr[u];
        }
        else
            G.ae(u, G.t, -scr[u]);
        
        REP(i, SZ(_adj[u])){
            if (!inD[v]) G.ae(v, u, INF);
        }
    }
    
}
#undef v



int main(){
    
#ifndef ONLINE_JUDGE
    freopen("/users/xiaodao/desktop/Exercise/in.txt", "r", stdin);
    //freopen("/users/xiaodao/desktop/Exercise/out.txt", "w", stdout);
#endif
    
    init();
    printf("%d\n", ans - G.sap());
}